The present invention generally relates to an internal combustion engine having a piston crank mechanism for reciprocating a piston, and more particularly, to a diesel engine or an inner-cylinder direct injection gasoline engine having such a piston crank mechanism.
Japanese Patent Application Publication No. 2001-227367 discloses a variable compression ratio mechanism of an internal combustion engine using a multilink piston crank mechanism, which was previously proposed by the applicant of the present application. This mechanism links a piston and a crankpin with each other by an upper link and a lower link. One end of the upper link is connected with the piston via a piston pin. The other end of the upper link is connected with the lower link via a first connection pin. The lower link is mounted rotatably on the crankpin of a crankshaft. This mechanism restrains movement of the lower link by a control link having one end connected with the lower link via a second connection pin. The other end of the control link is supported on a lower part of a cylinder block, for example, via a cam mechanism. The center of swinging motion of the other end of the control link can be shifted by the cam mechanism so as to vary a top dead center of the piston, and thereby vary a compression ratio of the engine.